The present invention is related to the field of pressure transducers, and more particularly, to capacitive or piezoresistive pressure transducers in which sensed pressure causes deflection of a pressure displaceable diaphragm so as to provide a predetermined capacitance or resistance variation of a pressure sensing element. This capacitance or resistance variation is then coupled to additional circuit electronics so as to provide an electrical signal representative of the sensed pressure. The combination of the pressure transducer and any additional external electronics is typically referred to as a "pressure sensor."
In pressure sensors utilizing either capacitive or resistive pressure transducers, typically problems have occurred with regard to providing a highly reliable interface connection between the actual pressure sensing element and the associated electronics. In some prior pressure transducers metallized vias or openings in a base substrate have been utilized to provide the interface connection between a pressure sensing capacitor element and additional external electronics. U.S. Pat. No. 4,384,899 to Myers illustrates such a configuration. In some instances, pins sealed in the base of a pressure transducer have been utilized to provide the interface connection between a pressure sensing element and external electronics.
Some pressure sensors have proposed utilizing a silicon diaphragm as the pressure sensing element and incorporating a plurality of semiconductor components on the silicon diaphragm wherein these components comprise at least some of the previously external electronics that respond to the capacitive or resistive change produced by deflection of the pressure sensing diaphragm. In such previously proposed structures, typically the silicon diaphragm is anodically bonded to a glass base. Preferably, the anodic bonding occurs in accordance with the manufacturing technique illustrated in U.S. Pat. No. 4,384,899 to Myers. However, generally in such sensors the input and output connections to the electronics synthesized on the silicon diaphragm are implemented by requiring conductor paths to extend laterally across anodically bonded areas of the diaphragm and glass base to external bonding pads provided on the diaphragm outside of the anodically bonded area. These lateral conductor paths inherently degrade the reliability of the hermetic seal between the diaphragm and the glass base which is intended to be provided by the anodic bonding process. Since the hermetic seal reliability is compromised, a less reliable pressure sensor is provided. This hermetic seal is used to protect the integrity of an interior cavity of the transducer in which a reference pressure is provided, and the seal also protects any interface connections formed between the diaphragm and base within the anodically-bonded area. Also, typically additional manufacturing steps, after anodic bonding, are required to provide electrical connection leads to the bonding pads.